Birth control has been around for decades, but all those options can sometimes be confusing. That’s particularly true when it comes to intrauterine devices (IUDs), which are becoming more and more popular due to their combination of wow factors.

You can keep an IUD in for up to three to 10 years, depending on the type you choose, and they’re over 99 percent effective at preventing pregnancy. For good reason, use of IUDs has increased from 1.5 percent of women ages 15 to 44 in 2002 to 7.2 percent of women in that age range in 2013, according to the Centers for Disease Control and Prevention. As an ob/gyn, this delights me to no end. I’m all for people finding the best birth control out there for them.

In over 10 years of counseling patients on how to do just that, I’ve seen many people who are interested in IUDs but have a laundry list of questions. One I hear often is, “Do I actually need to check my IUD strings?” Though it’s not the end of the world if you don’t, I—and many other doctors—recommend you do. Here’s why.

An IUD is a T-shaped device that goes into your uterus with strings extending through your cervix into your vagina. Those strings serve a few purposes.

As a quick primer, there are two types of IUDs: copper and hormonal. They both have great profiles for different people, although they’re different in how they prevent pregnancies. Copper IUDs work by creating an inflammatory, toxic reaction to sperm in the uterus. Hormonal IUDs use progestin to thicken cervical mucus and thin your endometrial (uterine) lining. Here’s more about the differences in IUDs and how to know which might be a good option for you.

No matter which type of IUD you get, your health care provider will insert the device by pushing it through your vagina, past your cervix, and into your uterus. The T-shaped part of the IUD will sit in your uterus, and the strings will trail through your cervix so that a small length of around 2 to 3 centimeters remains in your vagina.

The strings are there to help your health care provider confirm the location of the IUD once it’s placed, enable them to remove the IUD with ease when the time comes, and allow you to try to confirm your IUD’s placement on your own. Doing so is a good way of verifying that your IUD is exactly where it’s supposed to be, which is why I encourage my patients to check their strings monthly—at least for the first three months after insertion.

You might be wondering, Wait, where else could my IUD go? Good question.

One of the most common signs of expulsion is the IUD actually falling out, so you wouldn’t feel any strings inside of you in that instance. But sometimes the device does not fully expel, so you may feel the strings lower than expected and a hard portion of the device protruding from your cervix. In the (again, rare) case of expulsion, you would possibly also experience bleeding and cramping.

Then there’s perforation, when an IUD starts to migrate through the uterine walls. It’s also very rare, happening in an estimated 1 out of every 1,000 people with IUDs, and it can cause abdominal pain or severe pelvic cramping. Or, in some cases you might not feel that anything is physically awry but also not be able to feel your strings, so you go to your ob/gyn and find out the IUD has moved because the doctor sees as much on an ultrasound.

If you’re concerned about not feeling strings during a self-exam, and if you have excessive spotting or bleeding, change in vaginal discharge, or pain with intercourse, I would advise you to make an appointment with your ob/gyn to have an exam. Otherwise, let’s go over how to check those strings, shall we?

Checking your strings is simple: Insert a finger into your vagina and feel up toward your cervix. They will usually feel like thin bits of fishing line.

It helps to know what the strings feel like before you try to find them, so don’t feel too shy to ask if you can touch them before your IUD is inserted.

Once you do brush up against your strings, you might be shocked by how close to your vaginal entrance they seem. Aren’t they supposed to be way up by your cervix? The truth is that your cervix can move lower and higher depending on your menstrual cycle and the amount of blood flowing to your uterus. This does not change the effectiveness of the IUD and will not increase the risk of it falling out or perforating your uterus.

On the other hand, you might not feel the strings at all when you try to check them. Definitely not something to freak out about! Once the IUD is placed, the strings can “curl up” around the cervix so they’re flush against it or in a location you cannot feel with your fingers. This will not decrease how well your IUD works or make complications more likely.

Issues like expulsion and perforation are most common in the period soon after insertion, which is why I recommend my patients check their strings for a minimum of three months after getting their IUDs.

You can continue to check after that if it eases your mind or if you simply find it interesting to get to know your body a little bit better.

Jessica Shepherd, M.D., is an ob/gyn, women's health expert, and also the founder of Her Viewpoint, an online women's health forum that focuses on addressing taboo topics in a comfortable setting. As an ob/gyn, she practices at Baylor University Medical Center in Dallas, Texas. Dr. Shepherd is also seen regularly as an expert on TV and radio.